1. Field
Embodiments relate to an electro-photographic image forming apparatus. More particularly, embodiments relate to an image forming apparatus configured to easily and efficiently drive a plurality of photosensitive drums.
2. Description of the Related Art
Generally, an electro photographic image forming apparatus is an apparatus which prints an image by scanning light onto an image carrier charged by a predetermined potential to form an electrostatic latent image, developing the electrostatic latent image with a predetermined color toner, and then transferring and fixing the developed image onto a print medium.
A color electro photographic image forming apparatus for printing color images includes a plurality of developing units corresponding to a plurality of colors, for example, yellow, magenta, cyan, and black color developing units, and allows images formed by the developing units to be overlapped, thereby forming a full color image.
At this time, color matching, namely, color registration that each of color images developed in the developing units is placed in a right position is essentially required to implement a full-color image.
In order to improve the color registration, two methods are commonly used.
One method is to drive four developing units using a single motor. In this case, photosensitive media of the four developing units are driven by connecting a plurality of gear trains to the single motor. However, because speeds of the four photosensitive media depend on precision of the gear trains, this structure generates a phenomenon in that linear speeds of surfaces of the photosensitive media do not match each other. Accordingly, this method manages the color registration by managing machining tolerances, assembly tolerances, etc. of gears, etc. However, there is a limitation in the management of the color registration.
The other method is that each of the four developing units has an independent driving system and each of the photosensitive media is independently controlled. This method can achieve high color registration so that picture quality is good, but manufacturing cost is expensive.
Accordingly, an image forming apparatus that can improve the color registration and can reduce the manufacturing cost has been required.